<?php
/*
+--------------------------------------------------------------------------
|   WeCenter [#RELEASE_VERSION#]
|   ========================================
|   by WeCenter Software
|   © 2011 - 2014 WeCenter. All Rights Reserved
|   http://www.wecenter.com
|   ========================================
|   Support: WeCenter@qq.com
|
+---------------------------------------------------------------------------
*/

class core_upload {

    public $max_size                = 0;
    public $max_width               = 0;
    public $max_height              = 0;
    public $max_filename            = 0;
    public $allowed_types           = '';
    public $file_temp               = '';
    public $file_name               = '';
    public $orig_name               = '';
    public $file_type               = '';
    public $file_size               = '';
    public $file_ext                = '';
    public $upload_path             = '';
    public $overwrite               = FALSE;
    public $encrypt_name            = TRUE;
    public $is_image                = FALSE;
    public $image_width             = '';
    public $image_height            = '';
    public $image_type              = '';
    public $image_size_str          = '';
    public $error_code              = false;
    public $mimes                   = array();
    public $remove_spaces           = TRUE;
    public $xss_clean               = FALSE;
    public $temp_prefix             = "temp_file_";
    public $client_name             = '';

    protected $_file_name_override  = '';

    // --------------------------------------------------------------------

    /**
     * Initialize preferences
     *
     * @param   array
     * @return  void
     */
    public function initialize($config = array())
    {
        $defaults = array(
            'max_size'          => 0,
            'max_width'         => 0,
            'max_height'        => 0,
            'max_filename'      => 0,
            'allowed_types'     => '',
            'file_temp'         => '',
            'file_name'         => '',
            'orig_name'         => '',
            'file_type'         => '',
            'file_size'         => '',
            'file_ext'          => '',
            'upload_path'       => '',
            'overwrite'         => FALSE,
            'encrypt_name'      => TRUE,
            'is_image'          => FALSE,
            'image_width'       => '',
            'image_height'      => '',
            'image_type'        => '',
            'image_size_str'    => '',
            'error_code'        => false,
            'mimes'             => array(),
            'remove_spaces'     => TRUE,
            'xss_clean'         => TRUE,
            'temp_prefix'       => "temp_file_",
            'client_name'       => ''
        );


        foreach ($defaults as $key => $val)
        {
            if (isset($config[$key]))
            {
                $method = 'set_'.$key;

                if (method_exists($this, $method))
                {
                    $this->$method($config[$key]);
                }
                else
                {
                    $this->$key = $config[$key];
                }
            }
            else
            {
                $this->$key = $val;
            }
        }

        // if a file_name was provided in the config, use it instead of the user input
        // supplied file name for all uploads until initialized again
        $this->_file_name_override = $this->file_name;

        return $this;
    }

    // --------------------------------------------------------------------

    /**
     * Perform the file upload
     *
     * $filed file name or $_FILES field name, $data_stream are file data string
     *
     * @param   string
     * @param   string
     * @return  bool
     */
    public function do_upload($field = 'userfile', $data_stream = null)
    {
        // Is the upload path valid?
        if ( ! $this->validate_upload_path())
        {
            // errors will already be set by validate_upload_path() so just return FALSE
            return FALSE;
        }

        clearstatcache();

        if ($data_stream)
        {
            $tmp_file = TEMP_PATH . 'xhr_' . md5($field . microtime(TRUE) . rand(1, 999)) . '.stream';

            if (!file_put_contents($tmp_file, $data_stream))
            {
                $this->set_error('upload_unable_to_write_file');

                return FALSE;
            }

            // Set the uploaded data as class variables
            $this->file_temp = $tmp_file;
            $this->file_size = strlen($data_stream);

            $this->file_mime_type(array(
                'tmp_name' => $tmp_file,
                'type' => 'application/octet-stream'
            ));

            $this->file_type = preg_replace("/^(.+?);.*$/", "\\1", $this->file_type);
            $this->file_type = strtolower(trim(stripslashes($this->file_type), '"'));

            $this->file_name = $this->prep_filename($field);

            $this->file_ext  = $this->get_extension($this->file_name);
            $this->client_name = $this->file_name;
        }
        else
        {
            // Is $_FILES[$field] set? If not, no reason to continue.
            if ( ! isset($_FILES[$field]))
            {
                $this->set_error('upload_no_file_selected');
                return FALSE;
            }

            // Was the file able to be uploaded? If not, determine the reason why.
            if ( ! is_uploaded_file($_FILES[$field]['tmp_name']))
            {
                $error = ( ! isset($_FILES[$field]['error'])) ? 4 : $_FILES[$field]['error'];

                switch($error)
                {
                    case 1: // UPLOAD_ERR_INI_SIZE
                        $this->set_error('upload_file_exceeds_limit');
                        break;
                    case 2: // UPLOAD_ERR_FORM_SIZE
                        $this->set_error('upload_file_exceeds_form_limit');
                        break;
                    case 3: // UPLOAD_ERR_PARTIAL
                        $this->set_error('upload_file_partial');
                        break;
                    case 4: // UPLOAD_ERR_NO_FILE
                        $this->set_error('upload_no_file_selected');
                        break;
                    case 6: // UPLOAD_ERR_NO_TMP_DIR
                        $this->set_error('upload_no_temp_directory');
                        break;
                    case 7: // UPLOAD_ERR_CANT_WRITE
                        $this->set_error('upload_unable_to_write_file');
                        break;
                    case 8: // UPLOAD_ERR_EXTENSION
                        $this->set_error('upload_stopped_by_extension');
                        break;
                    default :   $this->set_error('upload_no_file_selected');
                        break;
                }

                return FALSE;
            }

            // Set the uploaded data as class variables
            $this->file_temp = $_FILES[$field]['tmp_name'];
            $this->file_size = $_FILES[$field]['size'];
            $this->file_mime_type($_FILES[$field]);
            $this->file_type = preg_replace("/^(.+?);.*$/", "\\1", $this->file_type);
            $this->file_type = strtolower(trim(stripslashes($this->file_type), '"'));

            $this->file_name = $this->prep_filename($_FILES[$field]['name']);
            $this->file_ext  = $this->get_extension($this->file_name);
            $this->client_name = $this->file_name;
        }

        // Is the file type allowed to be uploaded?
        if ( ! $this->is_allowed_filetype())
        {
            $this->set_error('upload_invalid_filetype');
            return FALSE;
        }

        // if we're overriding, let's now make sure the new name and type is allowed
        if ($this->_file_name_override != '')
        {
            $this->file_name = $this->prep_filename($this->_file_name_override);

            // If no extension was provided in the file_name config item, use the uploaded one
            if (strpos($this->_file_name_override, '.') === FALSE)
            {
                $this->file_name .= $this->file_ext;
            }

            // An extension was provided, lets have it!
            else
            {
                $this->file_ext  = $this->get_extension($this->_file_name_override);
            }

            if ( ! $this->is_allowed_filetype(TRUE))
            {
                $this->set_error('upload_invalid_filetype');
                return FALSE;
            }
        }

        // Convert the file size to kilobytes
        if ($this->file_size > 0)
        {
            $this->file_size = round($this->file_size/1024, 2);
        }

        // Is the file size within the allowed maximum?
        if ( ! $this->is_allowed_filesize())
        {
            $this->set_error('upload_invalid_filesize');
            return FALSE;
        }

        // Are the image dimensions within the allowed size?
        // Note: This can fail if the server has an open_basdir restriction.
        if ( ! $this->is_allowed_dimensions())
        {
            $this->set_error('upload_invalid_dimensions');
            return FALSE;
        }

        // Sanitize the file name for security
        $this->file_name = $this->clean_file_name($this->file_name);

        // Truncate the file name if it's too long
        if ($this->max_filename > 0)
        {
            $this->file_name = $this->limit_filename_length($this->file_name, $this->max_filename);
        }

        // Remove white spaces in the name
        if ($this->remove_spaces == TRUE)
        {
            $this->file_name = preg_replace("/\s+/", "_", $this->file_name);
        }

        /*
         * Validate the file name
         * This function appends an number onto the end of
         * the file if one with the same name already exists.
         * If it returns false there was a problem.
         */
        $this->orig_name = $this->file_name;

        if ($this->overwrite == FALSE)
        {
            $this->file_name = $this->set_filename($this->upload_path, $this->file_name);
        }

        /*
         * Run the file through the XSS hacking filter
         * This helps prevent malicious code from being
         * embedded within a file.  Scripts can easily
         * be disguised as images or other file types.
         */
        if ($this->xss_clean)
        {
            if ($this->do_xss_clean() === FALSE)
            {
                $this->set_error('upload_unable_to_write_file');
                return FALSE;
            }
        }

        if ($data_stream)
        {
            /*if ( ! @rename($this->file_temp, $this->upload_path.$this->file_name))
            {
                $this->set_error('upload_destination_error');
                return FALSE;
            }*/

            $file_temp = fopen($this->file_temp, 'r');

            $target = fopen($this->upload_path.$this->file_name, 'w');

            fseek($file_temp, 0, SEEK_SET);

            if (!stream_copy_to_stream($file_temp, $target))
            {
                $this->set_error('upload_destination_error');
                return FALSE;
            }

            fclose($target);
            fclose($file_temp);

            @unlink($this->file_temp);

            if (!file_exists($this->upload_path.$this->file_name))
            {
                $this->set_error('upload_unable_to_write_file');
                return FALSE;
            }
        }
        else
        {
            /*
            * Move the file to the final destination
            * To deal with different server configurations
            * we'll attempt to use copy() first.  If that fails
            * we'll use move_uploaded_file().  One of the two should
            * reliably work in most environments
            */

            if ( ! @copy($this->file_temp, $this->upload_path.$this->file_name))
            {
                if ( ! @move_uploaded_file($this->file_temp, $this->upload_path.$this->file_name))
                {
                    $this->set_error('upload_destination_error');
                    return FALSE;
                }
            }
        }

        /*
         * Set the finalized image dimensions
         * This sets the image width/height (assuming the
         * file was an image).  We use this information
         * in the "data" function.
         */
        $this->set_image_properties($this->upload_path.$this->file_name);

        return TRUE;
    }

    // --------------------------------------------------------------------

    /**
     * Finalized Data Array
     *
     * Returns an associative array containing all of the information
     * related to the upload, allowing the developer easy access in one array.
     *
     * @return  array
     */
    public function data()
    {
        if (!file_exists($this->upload_path . $this->file_name))
        {
            return FALSE;
        }

        return array (
                        'file_name'         => $this->file_name,
                        'file_type'         => $this->file_type,
                        'file_path'         => $this->upload_path,
                        'full_path'         => $this->upload_path.$this->file_name,
                        'raw_name'          => str_replace($this->file_ext, '', $this->file_name),
                        'orig_name'         => $this->orig_name,
                        'client_name'       => $this->client_name,
                        'file_ext'          => $this->file_ext,
                        'file_size'         => $this->file_size,
                        'is_image'          => $this->is_image(),
                        'image_width'       => $this->image_width,
                        'image_height'      => $this->image_height,
                        'image_type'        => $this->image_type,
                        'image_size_str'    => $this->image_size_str,
                    );
    }

    // --------------------------------------------------------------------

    /**
     * Set Upload Path
     *
     * @param   string
     * @return  void
     */
    public function set_upload_path($path)
    {
        // Make sure it has a trailing slash
        $this->upload_path = rtrim($path, '/').'/';
    }

    // --------------------------------------------------------------------

    /**
     * Set the file name
     *
     * This function takes a filename/path as input and looks for the
     * existence of a file with the same name. If found, it will append a
     * number to the end of the filename to avoid overwriting a pre-existing file.
     *
     * @param   string
     * @param   string
     * @return  string
     */
    public function set_filename($path, $filename)
    {
        if ($this->encrypt_name == TRUE)
        {
            $filename = md5(rand(1, 99999999) . microtime());

            if ( $this->is_image() )
            {
                $filename .= $this->file_ext;
            }

            if ( ! file_exists($path . $filename))
            {
                return $filename;
            }
            else
            {
                return $this->set_filename($path, $filename);
            }
        }

        return $filename;
    }

    // --------------------------------------------------------------------

    /**
     * Set Maximum File Size
     *
     * @param   integer
     * @return  void
     */
    public function set_max_filesize($n)
    {
        $this->max_size = ((int) $n < 0) ? 0: (int) $n;
    }

    // --------------------------------------------------------------------

    /**
     * Set Maximum File Name Length
     *
     * @param   integer
     * @return  void
     */
    public function set_max_filename($n)
    {
        $this->max_filename = ((int) $n < 0) ? 0: (int) $n;
    }

    // --------------------------------------------------------------------

    /**
     * Set Maximum Image Width
     *
     * @param   integer
     * @return  void
     */
    public function set_max_width($n)
    {
        $this->max_width = ((int) $n < 0) ? 0: (int) $n;
    }

    // --------------------------------------------------------------------

    /**
     * Set Maximum Image Height
     *
     * @param   integer
     * @return  void
     */
    public function set_max_height($n)
    {
        $this->max_height = ((int) $n < 0) ? 0: (int) $n;
    }

    // --------------------------------------------------------------------

    /**
     * Set Allowed File Types
     *
     * @param   string
     * @return  void
     */
    public function set_allowed_types($types)
    {
        if ( ! is_array($types) && $types == '*')
        {
            $this->allowed_types = '*';
            return;
        }

        if (strstr($types, '|'))
        {
            $this->allowed_types = explode('|', $types);
        }
        else
        {
            $this->allowed_types = explode(',', $types);
        }
    }

    // --------------------------------------------------------------------

    /**
     * Set Image Properties
     *
     * Uses GD to determine the width/height/type of image
     *
     * @param   string
     * @return  void
     */
    public function set_image_properties($path = '')
    {
        if ( ! $this->is_image())
        {
            return;
        }

        if (function_exists('getimagesize'))
        {
            if (FALSE !== ($D = @getimagesize($path)))
            {
                $types = array(1 => 'gif', 2 => 'jpeg', 3 => 'png');

                $this->image_width      = $D['0'];
                $this->image_height     = $D['1'];
                $this->image_type       = ( ! isset($types[$D['2']])) ? 'unknown' : $types[$D['2']];
                $this->image_size_str   = $D['3'];  // string containing height and width
            }
        }
    }

    // --------------------------------------------------------------------

    /**
     * Set XSS Clean
     *
     * Enables the XSS flag so that the file that was uploaded
     * will be run through the XSS filter.
     *
     * @param   bool
     * @return  void
     */
    public function set_xss_clean($flag = FALSE)
    {
        $this->xss_clean = ($flag == TRUE) ? TRUE : FALSE;
    }

    // --------------------------------------------------------------------

    /**
     * Validate the image
     *
     * @return  bool
     */
    public function is_image()
    {
        if (!in_array(strtolower($this->file_ext), array(
            '.jpg',
            '.jpe',
            '.jpeg',
            '.bmp',
            '.gif',
            '.png'
        )))
        {
            return FALSE;
        }

        // IE will sometimes return odd mime-types during upload, so here we just standardize all
        // jpegs or pngs to the same file type.

        $png_mimes  = array('image/x-png');
        $jpeg_mimes = array('image/jpg', 'image/jpe', 'image/jpeg', 'image/pjpeg');

        if (in_array($this->file_type, $png_mimes))
        {
            $this->file_type = 'image/png';
        }

        if (in_array($this->file_type, $jpeg_mimes))
        {
            $this->file_type = 'image/jpeg';
        }

        $img_mimes = array(
            'image/gif',
            'image/jpeg',
            'image/png',
        );

        return (in_array($this->file_type, $img_mimes, TRUE)) ? TRUE : FALSE;
    }

    // --------------------------------------------------------------------

    /**
     * Verify that the filetype is allowed
     *
     * @return  bool
     */
    public function is_allowed_filetype($ignore_mime = FALSE)
    {
        if ($this->allowed_types == '*')
        {
            return TRUE;
        }

        if (count($this->allowed_types) == 0 OR ! is_array($this->allowed_types))
        {
            $this->set_error('upload_no_file_types');
            return FALSE;
        }

        $ext = strtolower(ltrim($this->file_ext, '.'));

        if ( ! in_array($ext, $this->allowed_types))
        {
            return FALSE;
        }

        // Images get some additional checks
        $image_types = array('gif', 'jpg', 'jpeg', 'png', 'jpe');

        if (in_array($ext, $image_types))
        {
            if (getimagesize($this->file_temp) === FALSE)
            {
                return FALSE;
            }
        }

        return TRUE;
    }

    // --------------------------------------------------------------------

    /**
     * Verify that the file is within the allowed size
     *
     * @return  bool
     */
    public function is_allowed_filesize()
    {
        if ($this->max_size != 0  AND  $this->file_size > $this->max_size)
        {
            return FALSE;
        }
        else
        {
            return TRUE;
        }
    }

    // --------------------------------------------------------------------

    /**
     * Verify that the image is within the allowed width/height
     *
     * @return  bool
     */
    public function is_allowed_dimensions()
    {
        if ( ! $this->is_image())
        {
            return TRUE;
        }

        if (function_exists('getimagesize'))
        {
            $D = @getimagesize($this->file_temp);

            if ($this->max_width > 0 AND $D['0'] > $this->max_width)
            {
                return FALSE;
            }

            if ($this->max_height > 0 AND $D['1'] > $this->max_height)
            {
                return FALSE;
            }

            return TRUE;
        }

        return TRUE;
    }

    // --------------------------------------------------------------------

    /**
     * Validate Upload Path
     *
     * Verifies that it is a valid upload path with proper permissions.
     *
     *
     * @return  bool
     */
    public function validate_upload_path()
    {
        if ($this->upload_path == '')
        {
            $this->set_error('upload_no_filepath');
            return FALSE;
        }

        if (function_exists('realpath') AND @realpath($this->upload_path) !== FALSE)
        {
            $this->upload_path = str_replace("\\", "/", realpath($this->upload_path));
        }

        if (!defined('IN_SAE'))
        {
            if ( ! is_dir($this->upload_path))
            {
                if (! make_dir($this->upload_path))
                {
                    $this->set_error('upload_not_writable');

                    return FALSE;
                }
            }

            if ( ! is_really_writable($this->upload_path))
            {
                $this->set_error('upload_not_writable');

                return FALSE;
            }
        }

        $this->upload_path = preg_replace("/(.+?)\/*$/", "\\1/",  $this->upload_path);
        return TRUE;
    }

    // --------------------------------------------------------------------

    /**
     * Extract the file extension
     *
     * @param   string
     * @return  string
     */
    public function get_extension($filename)
    {
        $x = explode('.', $filename);
        return '.'.end($x);
    }

    // --------------------------------------------------------------------

    /**
     * Clean the file name for security
     *
     * @param   string
     * @return  string
     */
    public function clean_file_name($filename)
    {
        $bad = array(
                        "<!--",
                        "-->",
                        "'",
                        "<",
                        ">",
                        '"',
                        '&',
                        '$',
                        '=',
                        ';',
                        '?',
                        '/',
                        "%20",
                        "%22",
                        "%3c",      // <
                        "%253c",    // <
                        "%3e",      // >
                        "%0e",      // >
                        "%28",      // (
                        "%29",      // )
                        "%2528",    // (
                        "%26",      // &
                        "%24",      // $
                        "%3f",      // ?
                        "%3b",      // ;
                        "%3d"       // =
                    );

        $filename = str_replace($bad, '', $filename);

        return stripslashes($filename);
    }

    // --------------------------------------------------------------------

    /**
     * Limit the File Name Length
     *
     * @param   string
     * @return  string
     */
    public function limit_filename_length($filename, $length)
    {
        if (strlen($filename) < $length)
        {
            return $filename;
        }

        $ext = '';
        if (strpos($filename, '.') !== FALSE)
        {
            $parts      = explode('.', $filename);
            $ext        = '.'.array_pop($parts);
            //$filename = implode('.', $parts);
        }

        return substr($filename, 0, ($length - strlen($ext))).$ext;
    }

    // --------------------------------------------------------------------

    /**
     * Runs the file through the XSS clean function
     *
     * This prevents people from embedding malicious code in their files.
     * I'm not sure that it won't negatively affect certain files in unexpected ways,
     * but so far I haven't found that it causes trouble.
     *
     * @return  void
     */
    public function do_xss_clean()
    {
        $file = $this->file_temp;

        //  部分 IIS 环境下返回值始终为 0
        //if (filesize($file) == 0)
        if ($this->file_size == 0)
        {
            return FALSE;
        }


        if (function_exists('memory_get_usage') && memory_get_usage() && ini_get('memory_limit') != '')
        {
            $current = ini_get('memory_limit') * 1024 * 1024;

            // There was a bug/behavioural change in PHP 5.2, where numbers over one million get output
            // into scientific notation.  number_format() ensures this number is an integer
            // http://bugs.php.net/bug.php?id=43053

            $new_memory = number_format(ceil(filesize($file) + $current), 0, '.', '');

            @ini_set('memory_limit', $new_memory); // When an integer is used, the value is measured in bytes. - PHP.net
        }

        // If the file being uploaded is an image, then we should have no problem with XSS attacks (in theory), but
        // IE can be fooled into mime-type detecting a malformed image as an html file, thus executing an XSS attack on anyone
        // using IE who looks at the image.  It does this by inspecting the first 255 bytes of an image.  To get around this
        // CI will itself look at the first 255 bytes of an image to determine its relative safety.  This can save a lot of
        // processor power and time if it is actually a clean image, as it will be in nearly all instances _except_ an
        // attempted XSS attack.

        if (function_exists('getimagesize') && @getimagesize($file) !== FALSE)
        {
            if (($file = @fopen($file, 'rb')) === FALSE) // "b" to force binary
            {
                return FALSE; // Couldn't open the file, return FALSE
            }

            $opening_bytes = fread($file, 256);
            fclose($file);

            // These are known to throw IE into mime-type detection chaos
            // <a, <body, <head, <html, <img, <plaintext, <pre, <script, <table, <title
            // title is basically just in SVG, but we filter it anyhow

            if ( ! preg_match('/<(a|body|head|html|img|plaintext|pre|script|table|title)[\s>]/i', $opening_bytes))
            {
                return TRUE; // its an image, no "triggers" detected in the first 256 bytes, we're good
            }
            else
            {
                return FALSE;
            }
        }

        if (($data = @file_get_contents($file)) === FALSE)
        {
            return FALSE;
        }

        return $data;
    }

    // --------------------------------------------------------------------

    /**
     * Set an error message
     *
     * @param   string
     * @return  void
     */
    public function set_error($code)
    {
        $this->error_code = $code;
    }

    /**
     * Get an error message
     *
     * @return  array
     */
    public function get_error()
    {
        if ($this->error_code)
        {
            @unlink($this->file_temp);
        }

        return $this->error_code;
    }

    // --------------------------------------------------------------------

    /**
     * Prep Filename
     *
     * Prevents possible script execution from Apache's handling of files multiple extensions
     * http://httpd.apache.org/docs/1.3/mod/mod_mime.html#multipleext
     *
     * @param   string
     * @return  string
     */
    protected function prep_filename($filename)
    {
        if (strpos($filename, '.') === FALSE OR $this->allowed_types == '*')
        {
            return $filename;
        }

        $parts      = explode('.', $filename);
        $ext        = array_pop($parts);
        $filename   = array_shift($parts);

        foreach ($parts as $part)
        {
            if ( ! in_array(strtolower($part), $this->allowed_types))
            {
                $filename .= '.'.$part.'_';
            }
            else
            {
                $filename .= '.'.$part;
            }
        }

        $filename .= '.'.$ext;

        return $filename;
    }

    // --------------------------------------------------------------------

    /**
     * File MIME type
     *
     * Detects the (actual) MIME type of the uploaded file, if possible.
     * The input array is expected to be $_FILES[$field]
     *
     * @param   array
     * @return  void
     */
    protected function file_mime_type($file)
    {
        // We'll need this to validate the MIME info string (e.g. text/plain; charset=us-ascii)
        $regexp = '/^([a-z\-]+\/[a-z0-9\-\.\+]+)(;\s.+)?$/';

        /* Fileinfo extension - most reliable method
         *
         * Unfortunately, prior to PHP 5.3 - it's only available as a PECL extension and the
         * more convenient FILEINFO_MIME_TYPE flag doesn't exist.
         */
        if (function_exists('finfo_file'))
        {
            $finfo = finfo_open(FILEINFO_MIME);
            if (is_resource($finfo)) // It is possible that a FALSE value is returned, if there is no magic MIME database file found on the system
            {
                $mime = @finfo_file($finfo, $file['tmp_name']);
                finfo_close($finfo);

                /* According to the comments section of the PHP manual page,
                 * it is possible that this function returns an empty string
                 * for some files (e.g. if they don't exist in the magic MIME database)
                 */
                if (is_string($mime) && preg_match($regexp, $mime, $matches))
                {
                    $this->file_type = $matches[1];
                    return;
                }
            }
        }

        /* This is an ugly hack, but UNIX-type systems provide a "native" way to detect the file type,
         * which is still more secure than depending on the value of $_FILES[$field]['type'], and as it
         * was reported in issue #750 (https://github.com/EllisLab/CodeIgniter/issues/750) - it's better
         * than mime_content_type() as well, hence the attempts to try calling the command line with
         * three different functions.
         *
         * Notes:
         *  - the DIRECTORY_SEPARATOR comparison ensures that we're not on a Windows system
         *  - many system admins would disable the exec(), shell_exec(), popen() and similar functions
         *    due to security concerns, hence the function_exists() checks
         */
        if (DIRECTORY_SEPARATOR !== '\\')
        {
            $cmd = 'file --brief --mime ' . @escapeshellarg($file['tmp_name']) . ' 2>&1';

            if (function_exists('exec'))
            {
                /* This might look confusing, as $mime is being populated with all of the output when set in the second parameter.
                 * However, we only neeed the last line, which is the actual return value of exec(), and as such - it overwrites
                 * anything that could already be set for $mime previously. This effectively makes the second parameter a dummy
                 * value, which is only put to allow us to get the return status code.
                 */
                $mime = @exec($cmd, $mime, $return_status);
                if ($return_status === 0 && is_string($mime) && preg_match($regexp, $mime, $matches))
                {
                    $this->file_type = $matches[1];
                    return;
                }
            }

            if ( (bool) @ini_get('safe_mode') === FALSE && function_exists('shell_exec'))
            {
                $mime = @shell_exec($cmd);
                if (strlen($mime) > 0)
                {
                    $mime = explode("\n", trim($mime));
                    if (preg_match($regexp, $mime[(count($mime) - 1)], $matches))
                    {
                        $this->file_type = $matches[1];
                        return;
                    }
                }
            }

            if (function_exists('popen'))
            {
                $proc = @popen($cmd, 'r');
                if (is_resource($proc))
                {
                    $mime = @fread($proc, 512);
                    @pclose($proc);
                    if ($mime !== FALSE)
                    {
                        $mime = explode("\n", trim($mime));
                        if (preg_match($regexp, $mime[(count($mime) - 1)], $matches))
                        {
                            $this->file_type = $matches[1];
                            return;
                        }
                    }
                }
            }
        }

        // Fall back to the deprecated mime_content_type(), if available (still better than $_FILES[$field]['type'])
        if (function_exists('mime_content_type'))
        {
            $this->file_type = @mime_content_type($file['tmp_name']);
            if (strlen($this->file_type) > 0) // It's possible that mime_content_type() returns FALSE or an empty string
            {
                return;
            }
        }

        if (function_exists('getimagesize'))
        {
            $imageinfo = @getimagesize($file['tmp_name']);

            if ($imageinfo['mime'])
            {
                $this->file_type = $imageinfo['mime'];

                return;
            }
        }

        $this->file_type = $file['type'];
    }

    // --------------------------------------------------------------------

}
